Methods for constructing pre-coding matrix and feeding back index value and related communication devices

Abstract

The disclosure provides a method for constructing a three-dimensional (3D) multi-input multi-output (MIMO) pre-coding matrix, a method for feeding back index values of a 3D MIMO pre-coding matrix and related communication devices. The method for constructing a 3D MIMO pre-coding matrix comprises: constructing a first component matrix in a block diagonal form, wherein a diagonal sub-matrix of the first component matrix is a 3D beamforming sub-precoder for a two-dimensional (2D) antenna array; constructing a second component matrix which comprises phase weighting factors as matrix elements, wherein the phase weighting factors characterize coherent combination of signals from the 2D antenna array; and constructing the 3D MIMO pre-coding matrix according to the constructed first and second component matrixes. The method for feeding back index values of a 3D MIMO pre-coding matrix comprises: estimating a MIMO channel; and according to a result of the channel estimation, selecting and feeding back a first index value, a second index value and a third index value.

1 . A method for constructing a three-dimensional (3D) multi-input multi-output (MIMO) pre-coding matrix, comprising:
 constructing a first component matrix in a block diagonal form, wherein a diagonal sub-matrix of the first component matrix characterizes 3D beamforming for a two-dimensional (2D) antenna array;   constructing a second component matrix which comprises phase weighting factors as matrix elements, wherein the phase weighting factors characterize coherent combination of signals from the 2D antenna array; and   constructing the 3D MIMO pre-coding matrix according to the constructed first and second component matrixes.   
     
     
         2 . A method according to  claim 1 , wherein the diagonal sub-matrix of the first component matrix is a Kronecker product of a first discrete Fourier transform (DFT) vector and a second DFT vector. 
     
     
         3 . A method according to  claim 2 , wherein the first DFT vector and the second DFT vector are respectively applied to horizontal and vertical antenna arrays of the 2D antenna array. 
     
     
         4 . A method according to  claim 2 , wherein a set of the first DFT vectors, a set of the second DFT vectors and a set of the second component matrixes define a 3D MIMO pre-coding codebook. 
     
     
         5 . A method for feeding back index values of a three-dimensional (3D) multi-input multi-output (MIMO) pre-coding matrix, comprising:
 estimating a MIMO channel; and   according to a result of the channel estimation, selecting and feeding back a first index value, a second index value and a third index value so as to enable constructing a pre-coding matrix in a 3D MIMO pre-coding codebook according to the method of  claim 4 , wherein the first index value indicates a first DFT vector in a set of first DFT vectors, the second index value indicates a second DFT vector in a set of second DFT vectors, the third index value indicates a second component matrix in a set of second component matrixes.   
     
     
         6 . A communication device for constructing a three-dimensional (3D) multi-input multi-output (MIMO) pre-coding matrix, comprising:
 a first component matrix constructing unit configured to construct a first component matrix in a block diagonal form, wherein a diagonal sub-matrix of the first component matrix characterizes 3D beamforming for a two-dimensional (2D) antenna array;   a second component matrix constructing unit configured to construct a second component matrix which comprises phase weighting factors as matrix elements, wherein the phase weighting factors characterize coherent combination of signals from the 2D antenna array; and   a pre-coding matrix constructing unit configured to construct the 3D MIMO pre-coding matrix according to the constructed first and second component matrixes.   
     
     
         7 . A communication device according to  claim 6 , wherein the diagonal sub-matrix of the first component matrix is a Kronecker product of a first discrete Fourier transform (DFT) vector and a second DFT vector. 
     
     
         8 . A communication device according to  claim 7 , wherein the first DFT vector and the second DFT vector are respectively applied to horizontal and vertical antenna arrays of the 2D antenna array. 
     
     
         9 . A communication device according to  claim 7 , wherein a set of the first DFT vectors, a set of the second DFT vectors and a set of the second component matrixes define a 3D MIMO pre-coding codebook. 
     
     
         10 . A communication device according to  claim 6 , wherein the communication device is a transmitting point and/or a user equipment. 
     
     
         11 . A communication device according to  claim 10 , wherein the transmitting point is a base station. 
     
     
         12 . A communication device for feeding back index values of a three-dimensional (3D) multi-input multi-output (MIMO) pre-coding matrix, comprising:
 a channel estimation unit configured to estimate a MIMO channel; and   a feedback unit configured to, according to a result of the channel estimation, select and feed back a first index value, a second index value and a third index value so as to enable constructing a pre-coding matrix in a 3D MIMO pre-coding codebook according to the communication device of  claim 9 , wherein the first index value indicates a first DFT vector in a set of first DFT vectors, the second index value indicates a second DFT vector in a set of second DFT vectors, the third index value indicates a second component matrix in a set of second component matrixes.   
     
     
         13 . A communication device according to  claim 12 , wherein the communication device is a user equipment.